The proposed research is designed to determine the cause of incomplete luteinization of granulosa cells of post-ovulatory follicles of spotted skunks during the prolonged preimplantation period. We have previously demonstrated that corpora lutea are the source of a compound, which, in addition to progesterone, is essential for induction of nidation in ferrets. Moreover, we suspect that the corpora lutea of skunks and other carnivores serve as the source of this same compound. We therefore propose to determine the chemical nature of this compound in ferret corpora lutea and to determine whether it will induce early implantation in spotted skunks during the prolonged 200-220 day period of delayed implantation. Lastly we will attempt to determine whether prostaglandins are required for nidation in carnivores.